Assembly of hexaboride fine particles, hexaboride fine particle dispersion, hexaboride fine particle-dispersed body, laminated transparent base material using hexaboride fine particle-dispersed body, infrared-absorptive film, and infrared-absorptive glass

ABSTRACT

There is provided new transparent near infrared absorptive fine particles having a wide range of near infrared absorption, which are an assembly of hexaboride fine particles, wherein when a particle shape of the number of particles contained in the assembly is approximately regarded as a spheroid body, there are 20% or more and less than 80% of particles having an aspect ratio [(long axis length)/(short axis length)] of 1.5 or more and less than 5.0, and there are 20% or more and less than 80% of particles having an aspect ratio of 5.0 or more and less than 20.0.

TECHNICAL FIELD

The present invention relates to an assembly of hexaboride fineparticles, a hexaboride fine particle dispersion, a hexaboride fineparticle-dispersed body, a laminated transparent base material using thehexaboride fine particle-dispersed body, an infrared-absorptive film andan infrared-absorptive glass.

DESCRIPTION OF THE RELATED ART

Various techniques have been proposed as a heat ray-shielding techniqueof reducing a solar transmittance while having an excellent visiblelight transmittance and maintaining transparency. Above all, the heatray-shielding technique using a conductive fine particle-dispersed bodyhas a merit such as excellent heat ray-shielding properties, a low cost,a radio wave transparency, and further a high weather resistance, or thelike, compared with other techniques.

For example, patent document 1 discloses an infrared ray absorbingsynthetic resin molding formed by laminating on a transparent syntheticresin base material, a transparent resin containing a tin oxide finepowder in a dispersed state, and a material obtained by molding atransparent synthetic resin containing the tin oxide fine powder in adispersed state into a sheet or a film.

Also, patent document 2 discloses a laminated glass with an intermediatelayer interposed between at least two opposing plate glasses, theintermediate layer being formed in a dispersion state of metal such asSn, Ti, Si, Zn, Zr, Fe, Al, Cr, Co, Ce, In, Ni, Ag, Cu, Pt, Mn, Ta, W,V, and Mo, oxide of this metal, nitride of this metal, sulfide of thismetal, and the metal doped with Sb or F, or further a composite of them.

Further, patent document 3 to 5 disclose a selective permeable filmcoating solution in which titanium nitride fine particles or hexaboridefine particles are dispersed, a selectively permeable film, a heat rayshielding component dispersion, a heat ray shielding resin molded body,or the like.

-   Patent document 1: Japanese Patent Laid Open Publication No.    1990-136230-   Patent document 2: Japanese Patent Laid Open Publication No.    1996-259279-   Patent document 3: Japanese Patent Laid Open Publication No.    1999-181336-   Patent document 4: Japanese Patent Laid Open Publication No.    2000-96034-   Patent document 5: Japanese Patent Laid Open Publication No.    2004-162020

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

According to the investigation by the inventors of the presentinvention, it is found that a heat ray-shielding structure such as theinfrared absorptive synthetic resin molded product, etc., disclosed inpatent documents 1 and 2 has a problem that a shielding performance isnot sufficient when a high visible light transmittance is requested.

Here, the inventors of the present invention reach an idea of hexaboridefine particles as light absorbing fine particles and a dispersion of thehexaboride fine particles. That is, the inventors of the presentinvention obtain a knowledge that the hexaboride fine particles and thehexaboride fine particle dispersed body has a strong capability ofabsorbing near infrared while maintaining high transparency, at a lowcost while having a high molar extinction coefficient, and has a highweather resistance, and such hexaboride fine particles and dispersion ofthe hexaboride fine particles can be used as a light absorbing fineparticle dispersion and a light absorbing fine particle dispersed body.

Based on the above idea, the present applicant discloses theabovementioned patent documents 3 to 5, and provide a coating solutionfor selective transmission film, and a selective transmission film inwhich titanium nitride fine particles or hexaboride fine particles aredispersed, a heat ray-shielding component dispersed body, a heatray-shielding resin molding and the like.

However, as a result of further investigation by the inventors of thepresent invention, the following problem is found.

That is, the hexaboride fine particles disclosed in patent documents 3to 5 sometimes cannot sufficiently absorb the light having a highweighting coefficient in the wavelength of around 1000 nm in the solarlight. Therefore, when the concentration of the hexaboride fineparticles is increased so as to sufficiently absorb the light in thevicinity of the wavelength of 1000 nm, light in the visible light regionis also largely absorbed. For this reason, properties as a solarradiation shielding material that transmits visible light but shieldsthe solar light sometimes become insufficient.

In order to solve this problem, for example, patent document 4 disclosesa configuration in which light absorbing fine particles other thanhexaboride fine particles are mixed with hexaboride fine particles.However, mixing and using light-absorbing fine particles of differenttypes makes it difficult to select a dispersant capable of stablypresenting plural types of light-absorbing fine particles in a solventand select a method of addition, and furthermore, there is a possibilitythat aggregation of the light absorbing fine particles occurs duringmixture. As a result, there are various quality control problems suchthat a difficult mixing and dispersing operation must be sufficientlyperformed for the light absorbing fine particles and the dispersant; aninfluence on a medium such as the resin, etc., which will finallycontain the light absorbing fine particles is different in each type ofthe light absorbing fine particles; and a progress state of an agingvariation is different in each type of the light absorbing fineparticles.

Under the abovementioned circumstance, the present invention is made,and an object of the present invention is to provide an assembly ofhexaboride fine particles, a hexaboride fine particle dispersion, ahexaboride fine particle-dispersed body, a laminated transparent basematerial using the hexaboride fine particle-dispersed body, aninfrared-absorptive film, and an infrared-absorptive glass, in whichselectivity of an absorption wavelength is controlled and which has asufficient property as a solar radiation shielding material forshielding a solar light.

Means for Solving the Problem

In order to solve the abovementioned problem, inventors of the presentinvention perform intensive studies.

As a result, it is found that no consideration has been made on theconfiguration of controlling the shape of the fine particles inhexaboride fine particles known hitherto or in the hexaboride fineparticle-dispersed body according to the prior art in which thehexaboride fine particles are applied.

It is found that the reason why the hexaboride fine particles don'tsufficiently absorb the light having a high weighting coefficient in thevicinity of the wavelength of 1000 nm in the solar light, is that theshapes of the formed particles and the existence ratio of each shapedparticle are inappropriate, because control of the shape of theparticles is not taken into consideration in granulating the hexaboridefine particles.

For example, the abovementioned patent document 3 and patent document 5simply disclose a procedure of preparing a lanthanum boride fineparticle dispersion by mixing lanthanum boride fine particles (LaB₆)having an average particle size of 100 nm or less with an organicsolvent and a silane coupling agent, and performing ball mill mixturefor 100 hours using a zirconia ball having a diameter of 4 mm, and noparticular reference is made to the shape of the particles in the formof dispersions or coating films or dispersed bodies.

Further patent document 4 similarly discloses a procedure of preparingthe hexaboride fine particle dispersion by mixing the hexaboride fineparticles having an average particle size of 85 to 120 nm with anorganic solvent and a silane coupling agent, and performing ball millmixture using a zirconia ball having a diameter of 4 mm, and noparticular reference is made to the shape of the particles in the formof dispersions or a coating films or dispersed bodies.

Further, in other known document, the description regarding the controlof the particle shape of the hexaboride and the effect thereof does notsubstantially exceed a range of the description of patent documents 3 to5. That is, by adopting a configuration in which each fine particle ofthe hexaboride fine particles is controlled to have a predeterminedshape, light absorption property exhibited by the dispersed body whenthe hexaboride fine particle is used as the dispersed body, is not clearat all.

Here, the inventors of the present invention perform further intensivestudies based on the above recognition.

Although details are described later, when the aspect ratio of thehexaboride fine particles is considered, with the particle shape of thehexaboride fine particles regarded as a spheroid body, it is found thatthe hexaboride fine particles having the aspect ratio of 1.5 or more andless than 4.0 have a main absorption peak in the light with a wavelengthof 900 to 1000 nm. Accordingly, it is possible to efficiently shieldsolar light while transmitting visible light. However, it is also foundthat the hexaboride fine particles can not sufficiently absorb the lighthaving a wavelength of longer than 1100 nm where the weightingcoefficient of the solar light is high.

It is also found that the hexaboride fine particles having the aspectratio of 4.0 or more and less than 20.0 have a main absorption peak inthe light having a wavelength of 1000 to 2000 nm, so that visible lightcan be transmitted while sunlight can be efficiently shielded. However,it is also found that the hexaboride fine particles can not sufficientlyabsorb the light having a wavelength of 800 to 1000 nm where theweighting coefficient of the solar light is high.

On the other hand, the hexaboride fine particles having an aspect ratioof less than 1.5 have their main absorption peak at a wavelength of 700to 900 nm. Therefore, such hexaboride fine particles don't sufficientlyabsorb the light in the vicinity of the wavelength of 1,000 nm where thesolar light weighting coefficient is sufficiently high, and absorbs thelight in the visible light region. Therefore, properties as a solarradiation shielding material are not satisfactory.

Based on the above knowledge, it is found by the inventors of thepresent invention, that an assembly of hexaboride fine particles havinga wide absorption in a near infrared region where the solar lightweighting coefficient is high while transmitting visible light can beobtained, by mixing the hexaboride fine particles having the aspectratio of 1.5 or more and less than 4.0 and the hexaboride fine particleshaving the aspect ratio of 4.0 or more and less than 20.0 at apredetermined ratio to obtain the assembly.

Specifically, in the assembly of hexaboride fine particles or adispersed body thereof present within a field of view of a predeterminedTEM tomography image, the particle shape of the hexaboride fineparticles present in this field of view is regarded as a spheroid body,and the number of all hexaboride fine particles present in this field ofview is 100 (number) %, and the ratio of the numbers occupied by thehexaboride fine particles whose aspect ratio [(long axis length)/(shortaxis length)] value is 1.5 or more and less than 4.0 is set to a(number) %, and the ratio of the number occupied by the hexaboride fineparticles whose aspect ratio value is 4.9 or more and less than 10.0 isset to b (number) %. In this case, the values of a and b satisfy 60(number) %≦(a+b) (number) %≦100 (number) % and a:b=20:80 to 80:20. Inthis case, it is found that the solar radiation shielding property ofthe hexaboride fine particle assembly and the dispersed body in whichthe hexaboride fine particle assembly is dispersed is significantlysatisfactory.

In the present invention, the term “assembly” is used as a conceptindicating a state in which a plurality of fine particles having eachform exist in the same space and a state thereof. On the other hand,according to the present invention, the term “assembly” is not used as aconcept indicating the assembly formed by a plurality of fine particles,and the state thereof.

Namely, in order to solve the abovementioned problem, a first inventionis an assembly of hexaboride fine particles, wherein when a particleshape of the hexaboride fine particles contained in the assembly isregarded as a spheroid body, and when the number ratio of the hexaboridefine particles contained in the assembly and having an aspect ratio[(long axis length)/(short axis length)] of 1.5 or more and less than4.0 is expressed as a (number) %, and the number ratio of hexaboridefine particles contained in the assembly and having an aspect ratio[(long axis length)/(short axis length)] of 4.0 or more and less than20.0 is expressed as b (number) %, 60 (number) %≦(a+b) (number) %≦100(number) %, and a:b=20:80 to 80:20 are satisfied.

A second invention is the assembly of hexaboride fine particles of thefirst invention, wherein the hexaboride fine particles contained in theassembly of the hexaboride fine particles have an average dispersedparticle size of 1 nm or more and 100 nm or less.

A third invention is the assembly of hexaboride fine particles of thefirst invention or the second invention, wherein the hexaboride fineparticles are lanthanum hexaboride fine particles.

A fourth invention is a hexaboride fine particle dispersion, containingthe assembly of the hexaboride fine particles of any one of the first tothird inventions in a state of being dispersed in a liquid medium, theliquid medium being selected from water, an organic solvent, an oil andfat, a liquid resin, a liquid plasticizer for a plastic, or a mixture oftwo or more selected from them.

A fifth invention is the hexaboride fine particle dispersion of thefourth invention, wherein the assembly of the hexaboride fine particlesare contained in an amount of 0.02 mass % or more and 20 mass % or less.

A sixth invention is a hexaboride fine particle-dispersed body, whereinthe assembly of the hexaboride fine particles of any one of the firstinvention to the fourth invention are dispersed in a thermoplastic resinor a UV curable resin.

A seventh invention is the hexaboride fine particle-dispersed body ofthe sixth invention, wherein the thermoplastic resin is one kind ofresin selected from the group consisting of polyethylene terephthalateresin, polycarbonate resin, acrylic resin, styrene resin, polyamideresin, polyethylene resin, vinyl chloride resin, olefin resin, epoxyresin, polyimide resin, fluororesin, ethylene vinyl acetate copolymer,and polyvinyl acetal resin; or

a mixture of two or more kinds of resins selected from the resin group;or

a copolymer of two or more kinds of resins selected from the resingroup.

An eighth invention is the hexaboride fine particle-dispersed body ofthe sixth or seventh invention, wherein the assembly of the hexaboridefine particles are contained in an amount of 0.001 mass % or more and80.0 mass % or less.

A ninth invention is the hexaboride fine particle-dispersed body of anyone of the sixth to eighth inventions, wherein the hexaboride fineparticle-dispersed body has a sheet shape, a board shape, or a filmshape.

A tenth invention is the hexaboride fine particle-dispersed body of anyone of the sixth to ninth inventions, wherein the content of thehexaboride fine particle-dispersed body per unit projected areacontained in the hexaboride fine particle-dispersed body is 0.01 g/m² ormore and 0.5 g/m² or less.

An eleventh invention is a laminated transparent base material usinghexaboride fine particle-dispersed body, wherein the hexaboride fineparticle-dispersed body of any one of the sixth to tenth inventions ispresent between a plurality of transparent base materials.

A twelfth invention is an infrared absorptive film or an infraredabsorptive glass, wherein the hexaboride fine particle-dispersed body ofany one of the sixth to tenth inventions is provided as a coating layeron at least one side of a transparent base material selected from atransparent film base material or a transparent glass base material.

A thirteenth invention is an infrared absorptive film or an infraredabsorptive glass of the twelfth invention, wherein the resin is a UVcurable resin.

A fourteenth invention is the infrared absorptive film or the infraredabsorptive glass of the twelfth or thirteenth invention, wherein thethickness of the coating layer is 10 jtm or less.

A fifteenth invention is the infrared absorptive film of any one of thetwelfth to fourteenth inventions, wherein the transparent film basematerial is a polyester film.

A sixteenth invention is the infrared absorptive film or the infraredabsorptive glass of any one of the twelfth to fifteenth inventions,wherein the content of the assembly of the hexaboride fine particles perunit projected area included in the coating layer is 0.01 g/m² or moreand 0.5 g/m² or less.

Advantage of the Invention

The hexaboride fine particle assembly, the hexaboride fine particledispersion, the hexaboride fine particle-dispersed body, the transparentbase material using the hexaboride fine particle-dispersed body, and theinfrared absorptive film and the infrared absorptive glass, have wideabsorption properties in the near infrared wavelength region while usingthe hexaboride fine particles, and have appropriate properties as asolar radiation shielding material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a TEM tomography image of an assembly dispersed in a lanthanumhexaboride fine particle-dispersed body according to example 1.

FIG. 2 shows a frequency distribution of an aspect ratio of hexaboridefine particles contained in the assembly dispersed in the lanthanumhexaboride fine particle-dispersed body according to example 1.

FIG. 3 is a graph showing optical properties of a dispersion accordingto an example and a comparative Example.

FIG. 4 is a TEM image of the lanthanum hexaboride fine particles at30000 times according to comparative example 1.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described hereafter in anorder of [a] Hexaboride fine particles, [b] Assembly of the hexaboridefine particles, [c] Method for producing the assembly of the hexaboridefine particles, [d] Hexaboride fine particle dispersion and a method forproducing the same, [e] Hexaboride fine particle dispersed body and amethod for producing the same, [f] Sheet-like or film-like hexaboridefine particle dispersed body and a method for producing the same, [g]Transparent base material using the hexaboride fine particle dispersedbody and a method for producing the same, and [h] Infrared absorptivefilm and infrared absorptive glass and a method for producing the same.

[a] Hexaboride Fine Particles

The hexaboride fine particles used in the present invention exhibitlight absorption by plasmon absorption in the near-infrared region. Itscomponent is represented by the general formula XB₆, and its shape has anonspherical shape. Here, element X is at least one element selectedfrom La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr andCa. Lanthanum hexaboride [LaB₆], cerium hexaboride [CeB₆], praseodymiumhexaboride [PrB₆], neodymium hexaboride [NdB₆], gadolinium hexaboride[GdB₆], terbium hexaboride [TbB₆], dysprosium hexaboride [DyB₆], holmiumhexaboride [HoB₆], yttrium hexaboride [YB₆], samarium hexaboride [SmB₆],europium hexaboride [EuB₆], erbium hexaboride [ErB₆], thulium hexaboride[TmB₆], ytterbium hexaboride [YbB₆], lutetium hexaboride [LuB₆],strontium hexaboride [SrB₆], calcium hexaboride [CaB₆] and the like canbe mentioned as representative ones. Among them, lanthanum hexaboride[LaB₆] is preferably used, because the intensity of a near infraredabsorption is higher than the intensity of a visible light absorption.

In the hexaboride fine particles used in the present invention, it ispreferable that the surface thereof is not oxidized, but usually it isoxidized slightly. In addition, it is inevitable that a certain extentof oxidation of the surface occurs in a dispersion process of hexaboridefine particles. However, even in this case, there is no change in theeffectiveness of exhibiting the near infrared shielding effect.Therefore, for example even the hexaboride fine particles whose surfaceis oxidized can be used as the hexaboride fine particles used in thepresent invention.

Further, as the hexaboride fine particles used in the present invention,the higher the integrity as a crystal is, the greater the heat rayshielding effect is. However, even in a case of the hexaboride fineparticles whose crystallinity is low and a broad diffraction peak isgenerated by X-ray diffraction, when the basic bond inside the fineparticle is composed of a bond between each metal and boron, the heatray shielding effect is exhibited, and such hexaboride fine particlescan be applied in the present invention. It should be noted that theratio of metal to boron as hexaboride need not be strictly 6, and may bein a range of 5.8 to 6.2.

[b] Assembly of the Hexaboride Fine Particles

The assembly of the hexaboride fine particles according to the presentinvention is composed of an assembly of hexaboride fine particles havinga particle shape in a predetermined range.

Here, the features of the hexaboride fine particles contained in theassembly of the hexaboride fine particles will be described withreference to FIG. 1 which is a TEM tomographic image of a lanthanumhexaboride fine particle assembly according to example 1 describedlater. As shown in the method for producing a hexaboride fine particledispersion and the method for producing a hexaboride fine particledispersed body, which will be described later, it is apparent that theproperties of the hexaboride fine particles contained in the assembly ofthe hexaboride fine particles coincide with the properties of thehexaboride fine particles in the hexaboride fine particle dispersion andthe hexaboride fine particle dispersed body.

First, the particle shape of the hexaboride fine particles contained inthe assembly is regarded as a spheroid body, and the aspect ratio [(longaxis length)/(short axis length)] of the hexaboride fine particles isconsidered.

At this time, when the number ratio of hexaboride fine particles havingthe aspect ratio of 1.5 or more and less than 4.0 contained in theassembly is expressed by a (number) %, and the number ratio of thehexaboride particles having the aspect ratio [(long axis length)/(shortaxis length)] of 4.0 or more and less than 20.0 is expressed by b(number) %, the value of (a+b) (number) % is 60 (number) % or more and100 (number) % or less. Then, the ratio of a:b is in a range of 20:80 to80:20, more preferably in a range of 30:70 to 70:30.

The aspect ratio of the hexaboride fine particles is obtained byidentifying individual hexaboride fine particles by a three-dimensionalimage obtained by the TEM tomography method and comparing the specificshape of the particle with a length scale of the three-dimensionalimage, and calculating the aspect ratio [(long axis length)/(short axislength)] for each hexaboride fine particle.

Specifically, 100 or more, preferably 200 or more hexaboride fineparticles are identified from the three-dimensional image. For eachidentified hexaboride fine particle, directions of the long axis and theshort axis are determined (mutually orthogonal axes have a long axis anda short axis), lengths of the long and short axes are measured and theaspect ratio is calculated from the measured value.

As described above, the hexaboride fine particles having the aspectratio of less than 1.5 have their main absorption peak in a wavelengthof 700 to 900 nm. For this reason, the light in the vicinity of 1100 nmwhere the solar light weighting coefficient is sufficiently high, is notsufficiently absorbed, and the light in the visible light region isabsorbed. Therefore, the properties as the solar radiation shieldingmaterial are not satisfactory.

On the other hand, the hexaboride fine particles having the aspect ratioof 1.5 or more and less than 4.0 have a main absorption peak in awavelength of 900 to 1000 nm. Therefore, while the solar light can beefficiently shielded while transmitting the visible light, it is notable to sufficiently absorb the light having a longer wavelength thanthe wavelength of 1100 nm where the weighting coefficient is high in thesolar light.

The hexaboride fine particles having the aspect ratio of 4.0 or more andless than 20.0 have a main absorption peak in light having a wavelengthof 1000 to 2000 nm and can efficiently shield the solar light whiletransmitting the visible light. However, it is still impossible tosufficiently absorb the light with a wavelength of 800 to 1000 nm wherethe weighting coefficient is high in the solar light.

There are almost no hexaboride fine particles having the aspect ratio of20.0 or more.

Based on the above knowledge, the inventors of the present inventionfound that when the value of (a+b) (number) % in the assembly of thehexaboride fine particles is 60 (number) % or more, and the value of theratio of a:b is in a range of 20:80 to 80:20, the assembly of thehexaboride fine particles of the present invention has wide absorptionproperties in the near infrared wavelength region while using thehexaboride fine particles as the light absorbing fine particles, andexhibits appropriate properties as the solar radiation shieldingmaterial.

[c] Method for Producing the Assembly of the Hexaboride Fine Particles

The assembly of the hexaboride fine particles of the present inventionand a method for producing the same will be described. The method forproducing the assembly of the hexaboride fine particles is not limitedto the example, but can be realized by a method capable of realizing theshape characteristic and a presence ratio of the fine particlesconstituting the assembly of the hexaboride fine particles of thepresent invention.

The hexaboride fine particles having an average particle size of 0.5 to5 μm are prepared, and injected into a mill (for example, a solventdiffusion mill), together with fine grinding media having a lowerhardness than the fine particles (hereinafter may be simply referred toas beads), dispersing medium (for example, organic solvents such asisopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone,methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycolmonomethyl ether acetate, and n-butyl acetate, etc.) and optionally asuitable dispersant (for example, a polymeric dispersant), to therebyperform a beads mill pulverization. At this time, while lowering theperipheral velocity of the mill compared to a normal pulverization (forexample, about 0.3 to 0.8 times of the normal operation), and in thepresence of a dispersing medium and optionally a suitable dispersant,wet pulverization is performed with a low shear force.

When the particle shape of hexaboride fine particles contained in theassembly of the hexaboride fine particles is regarded as a spheroid bodyby the wet pulverization with this low shear force, and when the ratioof the number of the hexaboride fine particles whose aspect ratio [(longaxis length)/(short axis length)] value contained in this assembly is1.5 or more and less than 4.0 is set to a (number) %, and the ratio ofthe number of the hexaboride fine particles whose aspect ratio [(longaxis length)/(short axis length)] value contained in this assembly is4.0 or more and less than 20.0 is set to b (number) %, the assemblysatisfying 60 (number) %≦(a+b) (number) %≦100 (number) % and a:b=20:80to 80:20 can be produced.

The reason why the assembly of the hexaboride fine particles of thepresent invention can be produced under the above-mentioned productionconditions is not clear. However, probably this is because by selectingthe hardness of the beads and the peripheral velocity of the bead millas described above, the mode of destruction of hexaboride fine particleshaving a cubic crystal structure and extremely high hardness is not insuch a manner as to give an impact such as to reach the entire particleto crush it, but in such a manner as to strip off scaly fragments.

On the other hand, the method for preparing coarse (for example, havinga particle size of 1 μm or more) hexaboride fine particles, and using apulverization medium harder than the fine particles, injecting thepulverization medium into the mill together with the dispersing mediumand the dispersant, and applying a high peripheral velocity to performwet-type pulverization with a strong shear force, is not preferable forproducing the assembly of the present invention.

This is because a plurality of nearly spherical particles having theaspect ratio of less than 1.5, is contained in the assembly ofhexaboride fine particles pulverized under such a strong load.

The reason why the hexaboride fine particles are close to sphericalparticles having the aspect ratio of less than 1.5 is that the mode ofdestruction regarding the hexaboride particles is not in such a manneras to peel off scaly fragments having a high aspect ratio from theparticle surface, but in such a manner as to apply an impact on thewhole particle to crush it.

On the other hand, when the wet-type pulverization is performed to theabovementioned coarse hexaboride fine particles with a low shear forcein the presence of the dispersing medium and the dispersant, using thepulverization medium having excessively lower hardness than the hardnessof the particle itself, the assembly of the fine particles having a highaspect ratio cannot be produced. This is because when the hardness ofthe pulverization medium is lower than the hardness of the hexaboridefine particles and the hardness difference between the hexaboride fineparticles and the pulverization medium is too large, the pulverizationmedium itself is pulverized by the hexaboride fine particles beforecausing the destruction mode to the hexaboride fine particles in such amanner as to peel off the scaly fragments from the surface of theparticle, and probably the pulverization force to be added on thehexaboride fine particles is lost.

From the above study, it is confirmed that by using the pulverizationmedium having a Vickers hardness of about ⅓ to ½ of the Vickers hardnessof hexaboride fine particles, the assembly of hexaboride fine particleshaving a predetermined aspect ratio can be efficiently produced.

Specifically, for example, Vickers hardness of the lanthanum hexaboride,which is a preferred example of the hexaboride, is 2770 kg/mm². However,the hardness of the pulverization medium suitable for efficientlyproducing the assembly of the hexaboride lanthanum fine particles of thepresent invention is about 920 kg/mm² to 1850 kg/mm². That is, zirconiabeads (1100 kg/mm² to 1300 kg/mm²), alumina beads (1000 kg/mm² to 1100kg/mm²) and the like are suitable. On the other hand, the hardness ofglass beads (about 550 kg/mm²) is too low, and the hardness of siliconcarbide beads (about 2300 kg/mm²) and diamond beads (about 7000 kg/mm²)is too high, and therefore they are not suitable.

Further, a bead mill is more suitable for a mill used for producing theassembly of the hexaboride fine particles as described above than a ballmill, a three-roll mill, and a sand mill. The ball mill, the three-rollmill, and the sand mill are often used to produce non-sphericalparticles (usually flat scaly particles) of metals or metal compoundssuch as aluminum and nickel. However, since the hexaboride fineparticles generally have very high hardness and rigidity and hardlycause plastic deformation, it may be very difficult to processhexaboride spherical fine particles into non-spherical particles byplastic deformation.

As described above, the method for producing the assembly of thehexaboride fine particles of the present invention has been described.The abovementioned manufacturing method is merely an example, and thehexaboride fine particles produced by a wet-type process capable ofcontrolling shape can be used, or the hexaboride fine particles producedby a plasma torch method capable of controlling the shape can also beused. In any case, when the assembly of the hexaboride fine particles isfinally formed, and when the particle shape of the hexaboride fineparticles contained in the assembly is regarded as a spheroid body, thenumber ratio of the hexaboride fine particles contained in the assemblyand having an aspect ratio [(long axis length)/(short axis length)] of1.5 or more and less than 4.0 is expressed as a (number) %, and thenumber ratio of hexaboride fine particles contained in the assembly andhaving an aspect ratio [(long axis length)/(short axis length)] of 4.0or more and less than 20.0 is expressed as b (number) %, 60 (number)%≦(a+b) (number) %≦100 (number) %, and a:b=20:80 to 80:20 are satisfied.Such a method can be suitably used.

The average particle size of the fine particles contained in theassembly of the hexaboride fine particles of the present invention ispreferably 200 nm or less. This is because when the average particlesize is 200 nm or less, light is not completely shielded by scatteringwhen it is formed into a hexaboride fine particle dispersed bodydescribed later, visibility in the visible light region is maintained,and at the same time transparency can be efficiently maintained.

In the hexaboride fine particles of the present invention, inparticular, when the transparency in the visible light region isemphasized, it is preferable to further consider reduction of scatteringdue to the hexaboride fine particles.

When reduction of scattering due to the hexaboride fine particles istaken into consideration, the average particle size of the hexaboridefine particles is preferably 100 nm or less. This is because when thedispersed particle size of the hexaboride fine particles is small,scattering of light in the visible light region with a wavelength of 400nm to 780 nm due to geometric scattering or Mie scattering is reduced.As a result of the reduction of the scattering of the light, it ispossible to avoid a situation in which the hexaboride fine particledispersed body described later becomes like a frosted glass, and cleartransparency cannot be obtained:

This is because when the average particle size of the hexaboride fineparticles is 100 nm or less, the geometric scattering or the Miescattering is reduced and the Rayleigh scattering region is formed. Inthe Rayleigh scattering region, the scattered light is reduced ininverse proportion to the sixth power of the particle size, so that thescattering is reduced as the average particle size of the hexaboridefine particles is decreased and the transparency is improved.Furthermore, when the average particle size of the hexaboride fineparticles is 50 nm or less, the scattered light is extremely small,which is preferable. From a viewpoint of avoiding scattering of thelight, it is preferable that the average particle size of the hexaboridefine particles is small, and when the average particle size is 1 nm ormore, industrial production is easy.

It is preferable that the surface of the hexaboride fine particles iscoated with an oxide containing at least one element selected from Si,Ti, Zr, and Al, because weather resistance can be further improved.

[d] Hexaboride Fine Particle Dispersion and a Method for Producing theSame

The hexaboride fine particle dispersion of the present invention can beobtained by dispersing the assembly of the hexaboride fine particles ofthe present invention in a liquid medium.

Hereinafter, a method for producing a hexaboride fine particledispersion will be described. In the present invention, the hexaboridefine particle dispersion may be simply referred to as “a dispersionliquid” in some cases.

By adding the assembly of the hexaboride fine particles of the presentinvention and optionally an appropriate amount of a dispersant, acoupling agent, a surfactant and the like to a liquid medium andperforming dispersion treatment thereto, the hexaboride fine particledispersion of the present invention can be obtained. The medium of thehexaboride fine particle dispersion is required to have a function formaintaining the dispersibility of the hexaboride fine particledispersion and the later-described hexaboride fine particle dispersedbody described later, and function for not allowing a defect to begenerated when the hexaboride fine particle dispersion is used.

(1) Medium

The medium is selected from water, organic solvent, oil and fat, liquidresin, liquid plasticizer, or a mixture of two or more selected fromthem, to thereby produce the hexaboride fine particle dispersion. As theorganic solvent satisfying the above requirements, various ones such asalcohol type, ketone type, hydrocarbon type, glycol type, water type andthe like can be selected. Specifically, alcohol solvents such asmethanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzylalcohol and diacetone alcohol; ketone solvents such as acetone, methylethyl ketone, 3-methyl propyl ketone, methyl isobutyl ketone,cyclohexanone and isophorone; ester-type solvents such asmethyl-methoxy-propionate; glycol derivatives such as ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, ethylene glycolisopropyl ether, propylene glycol monomethyl ether, propylene glycolmonoethyl ether, propylene glycol methyl ether acetate, propylene glycolethyl ether acetate; amides such as formamide, N-methylformamide,dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone;aromatic hydrocarbons such as toluene and xylene; and halogenhydrocarbons such as ethylene chloride and chlorobenzene, can bementioned. Among them, organic solvents having low polarity arepreferable, and in particular, isopropyl alcohol, ethanol,1-methoxy-2-propanol, dimethylketone, methyl ethyl ketone, methylisobutyl ketone, toluene, propylene glycol monomethyl ether acetate, andN-butyl acetate are preferable. These solvents may be used alone or incombination of two or more.

As the liquid resin, methyl methacrylate or the like is preferable. As aliquid plasticizer for plastics, plasticizers which are compounds ofmonohydric alcohols and organic acid esters, plasticizers which areester type such as polyhydric alcohol organic acid ester compounds,phosphorus such as organic phosphoric acid type plasticizer, etc., aregiven as preferable examples. Among them, triethylene glycol di-2-ethylhexanoate, triethylene glycol di-2-ethyl butyrate and tetraethyleneglycol di-2-ethyl hexionate are more preferable because of their lowhydrolyzability.

(2) Dispersant, Coupling Agent, and Surfactant

The dispersant, the coupling agent and the surfactant can be selectedaccording to the purpose of use, but it is preferable to have a groupcontaining amine, a hydroxyl group, a carboxyl group, or an epoxy groupas a functional group. These functional groups are adsorbed on thesurface of the hexaboride fine particles, prevent the aggregation of thehexaboride fine particles, and have an effect of homogeneouslydispersing the hexaboride fine particles even in the hexaboride fineparticle dispersed body described below.

Examples of the dispersant that can be preferably used include aphosphoric ester compound, a polymeric dispersant, a silane couplingagent, a titanate coupling agent, an aluminum coupling agent, and thelike, but are not limited thereto. Examples of the polymer dispersantinclude an acrylic polymer dispersant, a urethane polymer dispersant, anacrylic block copolymer polymer dispersant, a polyether dispersant, apolyester polymer dispersant, and the like.

The amount of the dispersant to be added is preferably in a range of 10parts by weight to 1000 parts by weight, and more preferably in a rangeof 20 parts by weight to 200 parts by weight based on 100 parts byweight of the assembly of the hexaboride fine particles. When the amountof the dispersant added falls within the above range, the aggregation ofthe hexaboride fine particles does not occur in the liquid, and adispersion stability is maintained.

The method of dispersion treatment can be arbitrarily selected frompublicly known methods as long as the hexaboride fine particle assemblyis homogeneously dispersed in the liquid medium, and it is possible touse methods such as bead mill, ball mill, sand mill, ultrasonicdispersion, etc.

In order to obtain a homogeneous hexaboride fine particle dispersion,various additives and dispersants may be added or the pH may beadjusted.

(3) Hexaboride Fine Particle Dispersion

The content of the hexaboride fine particles in the above-mentionedhexaboride fine particle dispersion is preferably 0.02 mass % to 20 mass%. When the content is 0.02 mass % or more, it can be suitably used forproduction of a coating film or a molded plastic body described below,and when the content is 20 mass % or less, industrial production iseasy. 0.5% by mass or more and 20% by mass or less is more preferable.

The hexaboride fine particle dispersion of the present invention inwhich such hexaboride fine particles are dispersed in the liquid mediumis placed in an appropriate transparent container and the transmittanceof light is measured as a function of the wavelength using aspectrophotometer. The hexaboride fine particle dispersion of thepresent invention has excellent optical properties optimal for thelaminated transparent base material using the hexaboride fine particledispersed body, the infrared absorptive glass, and the infraredabsorptive film described later, namely, having a main absorption peakin the vicinity of roughly 850 to 1300 nm wavelength wherein the ratioof a light absorbance at the absorption peak position to the lightabsorbance in the wavelength 550 nm [(absorbance of the light at theabsorption peak)/(absorbance at the wavelength 550 nm)] is 5.0 or moreand 12.0 or less.

In this measurement, the transmittance of the hexaboride fine particledispersion is easily adjusted by diluting it with a dispersion solventor an appropriate solvent compatible with the dispersion solvent.

[e] Hexaboride Fine Particle Dispersed Body and a Method for Producingthe Same

The hexaboride fine particle dispersed body is composed of thehexaboride fine particles and a thermoplastic resin or a UV curableresin.

The thermoplastic resin is not particularly limited, but preferablyincludes:

one kind of resin selected from the resin group of polyethyleneterephthalate resin, polycarbonate resin, acrylic resin, styrene resin,polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin,epoxy resin, polyimide resin, fluororesin, ethylene.vinyl acetatecopolymer, polyvinyl acetal resin;

a mixture of two or more kinds of resins selected from this resin group;or

a copolymer of two or more kinds of resins selected from this resingroup.

On the other hand, although there is no particular limit as the UVcurable resin, for example an acrylic UV curable resin can be suitablyused.

The amount of the hexaboride fine particles dispersed and contained inthe hexaboride fine particle dispersed body is preferably 0.001% by massor more and 80.0% by mass or less, and more preferably 0.01% by mass ormore and 70% by mass or less. When the hexaboride fine particles areless than 0.001% by mass, it is necessary to increase the thickness inorder to obtain an infrared shielding effect requiring the hexaboridefine particle dispersed body, and when the hexaboride fine particles arecontained exceeding 80% by mass, the ratio of the thermoplastic resincomponent in the hexaboride fine particle dispersed body is decreasedand the strength may be decreased in some cases.

From a viewpoint of obtaining the infrared shielding effect by thehexaboride fine particle dispersed body, the content of the hexaboridefine particles per unit projected area included in the hexaboride fineparticle dispersed body is 0.01 g/m² or more and 0.5 g/m² or less.Incidentally, the “content per unit projected area” corresponds to aweight (g) of the hexaboride fine particles contained in a thicknessdirection of the hexaboride fine particle dispersed body of the presentinvention per unit area (m²) through which light passes.

The hexaboride fine particle dispersed body can be processed into asheet shape, a board shape or a film shape, and can be applied tovarious uses.

A method for producing the hexaboride fine particle dispersed body willbe described below.

The hexaboride fine particle dispersion is mixed with the thermoplasticresin or the plasticizer and thereafter the solvent component isremoved, to thereby obtain a hexaboride fine particle dispersion powder(hereinafter sometimes simply referred to as a dispersion powder) whichis a dispersed body in which the hexaboride fine particles are dispersedat a high concentration in the thermoplastic resin and/or thedispersant, or the dispersion (hereinafter sometimes simply referred toas a plasticizer dispersion) in which the hexaboride fine particles aredispersed in the plasticizer at a high concentration. As a method forremoving the solvent component from the hexaboride fine particledispersion, it is preferable to dry the hexaboride fine particledispersion under reduced pressure. Specifically, the hexaboride fineparticle dispersion is dried under depressurization while stirring thehexaboride fine particle dispersion, to separate the dispersion powderor the plasticizer dispersion from the solvent component. As a deviceused for the depressurized drying, a vacuum agitating type dryer can bementioned, but it is not particularly limited as long as it is anapparatus having the above function. Further, a pressure value at thetime of depressurization in the drying step is appropriately selected.

By using the depressurized drying method, removal efficiency of thesolvent from the hexaboride fine particle dispersion liquid is improved,and the hexaboride fine particle dispersion powder and the plasticizerdispersion are not exposed to a high temperature for a long time, andtherefore the agglomeration of the hexaboride fine particles dispersedin the dispersion powder or in the plasticizer dispersion does notoccur, which is preferable. Further, productivity of the hexaboride fineparticle dispersion powder and the hexaboride fine particle plasticizerdispersion is increased, and an evaporated solvent can be easilyrecovered, which is preferable from a viewpoint of environmentalconsideration.

In the hexaboride fine particle dispersion powder or the hexaboride fineparticle plasticizer dispersion obtained after the drying step, theresidual solvent is preferably 5% by mass or less. This is because whenthe residual solvent is 5% by mass or less, bubbles are not generatedwhen the hexaboride fine particle dispersion powder or hexaboride fineparticle plasticizer dispersion is processed into, for example, thelaminated transparent base material using the hexaboride fine particledispersed body described later, and an outer appearance and opticalproperties are satisfactorily maintained.

In addition, a master batch can be obtained by dispersing the hexaboridefine particle dispersion or the hexaboride fine particle dispersionpowder in the resin and pelletizing the resin.

Further, the master batch can also be obtained by homogeneously mixingthe hexaboride fine particle dispersion and the hexaboride fine particledispersion powder, with a powdery or pelletized thermoplastic resin, andwith other additive as needed, and thereafter extruding the mixture by avented single or twin screw extruder, and processing it into a pellet bya method of cutting general melt-extruded strands. In this case, as theshape thereof, a cylindrical or prismatic shape can be mentioned. It isalso possible to use a so-called hot cut method of directly cutting meltextrudates. In this case, the cut material generally has a sphericalshape.

[f] Sheet-Like or Film-Like Hexaboride Fine Particle Dispersed Body anda Method for Producing the Same

By homogeneously mixing the hexaboride fine particle dispersion powder,the hexaboride fine particle dispersion or the master batch into thetransparent resin, the hexaboride fine particle dispersed boy having asheet shape, a board shape or a film shape of the present invention canbe produced. From the hexaboride fine particle dispersed body having thesheet shape, the board shape or the film shape, the laminatedtransparent substrate using the hexaboride fine particle dispersed body,the infrared absorptive film, and the infrared absorptive glass can beproduced.

When the hexaboride fine particle dispersed body having a sheet shape,the board shape or the film shape is produced, various thermoplasticresins can be used for the resin constituting the sheet or the film. Thehexaboride fine particle dispersed body having the sheet shape, theboard shape or the film shape is preferably a thermoplastic resin havingsufficient transparency.

Specifically, it is preferable to use the resin selected from the resingroup such as polyethylene terephthalate resin, polycarbonate resin,acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinylchloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin,ethylene, and vinyl acetate copolymer, or a mixture of two or more kindsof resins selected from this resin group, or a copolymer of two or morekinds of resins selected from this resin group.

Further, when a hexaboride fine particle dispersed body having the sheetshape, the board shape, or the film shape is used as an intermediatelayer, and when the thermoplastic resin constituting the board or thefilm alone does not have a sufficient flexibility or adhesion to thetransparent base material, for example, when the thermoplastic resin ispolyvinyl acetal resin, the plasticizer is preferably further added.

As the plasticizer, a substance used as the plasticizer for thethermoplastic resin of the present invention can be used. For example,as the plasticizer used for the infrared absorptive film composed ofpolyvinyl acetal resin, plasticizers which are compounds of monohydricalcohols and organic acid esters, plasticizers which are ester type suchas polyhydric alcohol organic acid ester compounds, and plasticizerswhich are phosphoric acid type such as an organic phosphoric acid typeplasticizer, are given. Both plasticizers are preferably in a liquidstate at room temperature. Among them, a plasticizer which is an estercompound synthesized from a polyhydric alcohol and a fatty acid ispreferable.

After the hexaboride fine particle dispersion powder or the hexaboridefine particle dispersion or the masterbatch, thermoplastic resin andoptionally plasticizer and other additives are kneaded, the kneadedproduct is extruded by an extrusion molding method, an injection moldingmethod or the like, and it is possible to produce, for example, asheet-like hexaboride fine particle dispersed body formed in a flat orcurved state.

Known methods can be used for forming the sheet-like or film-likehexaboride fine particle dispersed body. For example, a calendar rollmethod, an extrusion method, a casting method, an inflation method, orthe like can be used.

[g] Laminated Transparent Base Material Using the Hexaboride FineParticle Dispersed Body and a Method for Producing the Same

Explanation is given for a laminated transparent base material using thehexaboride fine particle dispersed body which is formed by interposingthe sheet-like, the board-like or the film-like hexaboride fine particledispersed body between a plurality of transparent base materialscomposed of a material such as glass plate or plastic as an intermediatelayer.

The laminated transparent base material using the hexaboride fineparticle dispersed body is obtained by interposing the intermediatelayer from both sides thereof using the transparent base material. Asthe transparent base material, a transparent plate glass in a visiblelight region, a plate-like plastic, a board-like plastic, or a film-likeplastic is used. The material of the plastic is not particularly limitedand can be selected according to the purpose of use, and as examplesthereof, polycarbonate resin, acrylic resin, polyethylene terephthalateresin, PET resin, polyamide resin, vinyl chloride resin, olefin resin,epoxy resin, polyimide resin, fluorine resin, and the like can be used.

The transparent base material using the hexaboride fine particledispersed body of the present invention can also be obtained byintegrally laminating a plurality of opposed transparent base materials,with the sheet-like, the board-like, or the film-like hexaboride fineparticle dispersed body of the present invention interposed therebetweenby a publicly-known method.

As the optical property of the sheet-like, the board-like, or thefilm-like hexaboride fine particle dispersed body or a light absorptionstructure of the present invention, the following point can be realized:when a visible light transmittance is 70%, a minimum value (minimumtransmittance) in the transmittance in a light wavelength region of 850to 1300 nm wavelength is 35% or less.

Here, it is easy to adjust the visible light transmittance to 70% byadjusting an addition amount of the abovementioned assembly of thehexaboride fine particles, dispersion powder, plasticizer dispersion, ormaster batch and further the film thickness of the film or the sheet,etc., when adjusting a concentration of the assembly of the hexaboridefine particles contained in the hexaboride fine particle dispersion, thedispersion powder, the plasticizer dispersion, or the master batch, anda resin composition.

[h] Infrared Absorptive Film and Infrared Absorptive Glass and a Methodfor Producing the Same

By forming the coating layer containing the assembly of the hexaboridefine particles on at least one surface of the transparent substrateselected from a substrate film or a substrate glass, using thehexaboride fine particle dispersion described above, an infraredabsorptive film or an infrared absorptive glass can be produced.

The abovementioned hexaboride fine particle dispersion is mixed withplastic or monomer to prepare a coating liquid, and a coating film isformed on the transparent base material by a known method, therebyproducing an infrared absorptive film or an infrared absorptive glass.

For example, the infrared absorptive film can be prepared as follows.

A medium resin is added to the abovementioned hexaboride fine particledispersion to obtain a coating liquid. After the coating liquid isapplied on the surface of a film base material, a solvent is evaporatedand the resin is cured by a predetermined method, it becomes possible toform a coating film in which the assembly of the hexaboride fineparticles is dispersed in the medium.

As the medium resin of the coating film, for example, a UV curing resin,a thermosetting resin, an electron beam curing resin, a room temperaturecuring resin, a thermoplastic resin and the like can be selectedaccording to the purpose of use. Specifically, polyethylene resin,polyvinyl chloride resin, polyvinylidene chloride resin, polyvinylalcohol resin, polystyrene resin, polypropylene resin, ethylene vinylacetate copolymer, polyester resin, polyethylene terephthalate resin,fluorine resin, polycarbonate resin, acrylic resin, or polyvinyl butyralresin can be mentioned.

These resins may be used alone or in combination. However, among themedia for the coating layer, it is particularly preferable to use the UVcurable resin binder from a viewpoint of productivity and equipmentcost.

It is also possible to use a binder using a metal alkoxide. As the metalalkoxide, alkoxides such as Si, Ti, Al, Zr and the like arerepresentative. The binder using these metal alkoxides can behydrolyzed/polycondensed by heating or the like to form a coating layercomposed of an oxide film.

In addition to the above method, the coating layer may be formed byapplying a hexoboride fine particle dispersion on the substrate film orthe substrate glass and thereafter applying a binder thereon using themedium resin or the metal alkoxides.

Incidentally, the abovementioned film base material is not limited tothe film shape, and it may be, for example, the board shape or the sheetshape. As the film base material, PET, acrylic, urethane, polycarbonate,polyethylene, ethylene vinyl acetate copolymer, vinyl chloride, fluorineresin and the like can be used according to various purposes of use.However, as the infrared absorptive film, a polyester film ispreferable, and a PET film is more preferable.

The surface of the film base material is preferably subjected to asurface treatment in order to realize easy adhesion of the coatinglayer. Further, in order to improve the adhesion between the glasssubstrate or the film base material and the coating layer, it is alsopreferable to form an intermediate layer on the glass substrate or onthe film base material, and form a coating layer on the intermediatelayer. The constitution of the intermediate layer is not particularlylimited, and it can be constituted by, for example, a polymer film, ametal layer, an inorganic layer (for example, an inorganic oxide layerof silica, titania, zirconia or the like), or an organic/inorganiccomposite layer.

The method for providing the coating layer on the substrate film or thesubstrate glass is not particularly limited as long as it is a methodcapable of uniformly coating the hexaboride fine particle dispersion onthe surface of the substrate. For example, a bar coating method, agravure coating method, a spray coating method, a dip coating method,and the like can be mentioned.

For example, according to the bar coating method using a UV curableresin, the coating film can be formed on the substrate film or thesubstrate glass using a wire bar having a bar number that can satisfythe purpose of forming a target thickness of the coating film and atarget content of the hexaboride fine particles, by applying the coatingliquid in which a liquid concentration and the additives are suitablyadjusted to have appropriate leveling properties on the substrate filmor the substrate glass. Then, the solvent contained in the coatingliquid is removed by drying and thereafter the coating liquid isirradiated with UV-ray so as to be cured, thereby forming the coatinglayer on the substrate film or the substrate glass. At this time, thedrying condition of the coating film varies depending on theingredients, the kind of the solvent and the use ratio, but usually itis about 20 seconds to 10 minutes at a temperature of 60° C. to 140° C.Ultraviolet irradiation is not particularly limited, and a UV exposuremachine such as an extra-high pressure mercury lamp can be suitablyused, for example.

In addition, it is possible to manipulate the adhesion between thesubstrate and the coating layer, the smoothness of the coating film atthe time of coating, the drying property of the organic solvent and thelike by the steps before and after the formation of the coating layer.As the steps before and after the formation of the coating layer, forexample, the steps of surface treatment of the substrate, a pre-bake(pre-heating of the substrate), a post bake (post-heating of thesubstrate), and the like can be mentioned and appropriately selected.The heating temperature in the pre-baking step and/or the post-bakingstep is preferably 80° C. to 200° C., and the heating time is preferably30 seconds to 240 seconds.

The thickness of the coating layer on the substrate film or on thesubstrate glass is not particularly limited, but in practice it ispreferably 10 μm or less, and more preferably 6 μm or less. This isbecause, when the thickness of the coating layer is 10 μm or less,sufficient pencil hardness is exerted to exhibit abrasion resistance,and additionally, at the time of volatilization of the solvent in thecoating layer and curing of the binder, occurrence of abnormality in thesteps such as warping of the substrate film, etc., can be avoided.

The optical properties of the manufactured infrared absorptive film andthe infrared absorptive glass are such that when the visible lighttransmittance is 70%, the minimum value (minimum transmittance) at thetransmittance in the light wavelength region of 850 to 1300 nm is 35% orless. In addition, it is easy to adjust the visible light transmittanceto 70%, by adjusting the concentration of the hexaboride fine particlesin the coating liquid or adjusting the film thickness of the coatingfilm.

For example, the content of the assembly of the hexaboride fineparticles per unit projected area included in the coating layer ispreferably 0.01 g/m² or more and 0.5 g/m² or less.

EXAMPLES

Hereinafter, the present invention will be specifically described withreference to examples, but the present invention is not limited to theseexamples.

In the optical properties of the film of this example, the transmittanceof light in the wavelength range of 300 nm to 1600 nm was measured atintervals of 5 nm using a spectrophotometer (U-4100 manufactured byHitachi, Ltd.). The visible light transmittance was measured inaccordance with JIS R 3106.

Then, a wavelength where the absorbance of the film of this example ismaximum (described as “absorption peak wavelength” in this specificationin some cases), and a half-value width at an absorption peak having theabsorption peak wavelength (described as a “full width at half maximum”in this specification in some cases) in the wavelength range of 380 nmto 1600 nm, were obtained using a absorbance curve calculated by amethod described later.

The particle size was measured with a particle size distribution meter(Nanotrac UPA manufactured by Nikkiso Co., Ltd.).

When the absorption peak wavelength and the full width at half maximumthereof were determined, an evaluation was performed in the wavelengthrange of 380 nm to 1600 nm in the measurement range of the opticalproperties ranging from 300 nm to 1600 nm described above. This isbecause, first, the light absorption properties in the wavelength rangeof 300 nm to 380 nm has almost no relation to the optical properties asthe infrared ray absorbing material of the film of this example.Secondly, the light absorption properties in this range are hardlychanged even when there is a difference in shape and distribution ofhexaboride fine particles.

Example 1

10 parts by weight of fine particles of lanthanum hexaboride (LaB₆)particles (average particle size 1 to 3 μm, and sometimes described as“hexaboride α” in the present specification), 80 parts by weight oftoluene, 10 parts by weight of a dispersant (acrylic polymer dispersanthaving an amino group) were mixed to prepare 3 kg of a slurry. Thisslurry was charged into the bead mill together with the beads, and theslurry was circulated and pulverized and dispersed for 30 hours.

The used bead mill was a horizontal cylindrical annular type(manufactured by Ashizawa Co., Ltd.), and the material of an inner wallof a vessel and a rotor (rotary stirring part) was ZrO₂. As the beads,beads made of YSZ (Yttria-Stabilized Zirconia: yttria-stabilizedzirconia) having a diameter of 0.3 mm were used. Then, pulverization anddispersion processing was performed at a slurry flow rate of 1kg/minute.

In addition, by setting the rotation speed of the rotor at 6 m/sec andmaking it slower than usual producing conditions, it was possible tocontrol the destruction mode of the hexaboride α and to control theassembly of the hexaboride fine particles contained in the fine particledispersion of the hexaboride α in such a manner that when the numberratio of the hexaboride fine particles having an aspect ratio of 1.5 ormore and less than 4.0 was expressed as a (number) %, and the numberratio of the hexaboride fine particles having an aspect ratio of 4.0 ormore and less than 20.0 was expressed as b (number) %, 60 (number) % S(a+b) (number) % s 100 (number) % and a:b=20:80 to 80:20 were satisfied.

The average dispersed particle size of the hexaboride α in the obtainedhexaboride α dispersion (sometimes referred to as “dispersion A” in thepresent specification) was measured and found to be 25 nm.

A dried body of the dispersion A was observed by three-dimensional imageanalysis using TEM tomography.

First, FIG. 1 shows an example of an image in which the shape ofhexaboride present on the cross-section is drawn in a cross-sectionalarea of 500 nm square, from a three-dimensional image of hexaborideα-dispersed body obtained by TEM tomography.

Next, a three-dimensional image of 218 hexaboride α particles wasanalyzed, and the frequency distribution of the aspect ratio wasmeasured. The results are shown in FIG. 2. Here, in FIG. 2, thehorizontal axis represents the aspect ratio value and the vertical axisrepresents an existence frequency value.

According to the above measurement, it was found that 36.2 (number) ofhexaboride α fine particles having the aspect ratio of 1.5 or more andless than 4.0, and 63.3 (number) % of hexaboride α fine particles havingthe aspect ratio of 4.0 or more and less than 20.0, were contained inthe dispersion A.

Next, the optical properties of the dispersion A were measured.Specifically, the procedure was as follows.

In the dispersion A, toluene was added so that the concentration ofhexaboride α was 0.002 mass %, diluted, mixed, and shaken well.Thereafter, the diluted solution was placed in a glass cell having anoptical path length of 1 cm, and its transmittance curve was measuredwith a spectroscope. At this time, the baseline of the spectroscope waspulled with a sample filled with toluene in the same glass cell. Then,the transmittance curve was converted into an absorption curve by thefollowing equation 1.

A(λ)=−log 10(T(λ)/100)  Formula 1

Wherein, A (λ) is an absorption curve showing that the absorbance Adepends on a wavelength λ, and T(λ) is a transmittance curve showingthat the transmittance depends on a wavelength λ.

As a result, the absorption peak wavelength of the dispersion Aaccording to example 1 was 985 nm, and the full width at half maximum ofthe absorption peak was 400 nm. The obtained absorption curve is shownby a solid line in FIG. 3.

Comparative Example 1

The assembly of spherical lanthanum hexaboride fine particles (sometimesreferred to as “fine particle β” in the present specification) having avalue of the aspect ratio [(long axis length)/(short axis length)] of1.0 or more and 1.5 or less when the particle shape was approximated asa spheroid body, was prepared.

Fine particle β is a single phase of lanthanum hexaboride. FIG. 4 showsa TEM image of 30000 times magnification of the fine particle 3.

10 parts by weight of fine particles 0, 80 parts by weight of tolueneand 10 parts by weight of dispersant (acrylic polymer dispersant havingamino group) were mixed to prepare 3 kg of slurry. This slurry wascharged into a medium stirring mill together with beads, and the slurrywas circulated and pulverized and dispersed for 10 hours to obtain adispersion (sometimes referred to as “dispersion B” in the presentspecification).

The medium stirring mill used was a horizontal cylindrical annular type(manufactured by Ashizawa Co., Ltd.), and the material of the inner wallof the vessel and the rotor (rotary stirring part) was ZrO₂. For thebeads, beads made of YSZ having a diameter of 0.3 mm were used. Therotation speed of the rotor was 13 m/sec, and the pulverization anddispersion treatment was performed at a slurry flow rate of 1 kg/min.

The average dispersed particle size of the hexaboride fine particles inthe obtained dispersion B was measured to be 29 nm.

Next, the same operation as the dispersion A in example 1 was performed,and the optical properties of the dispersion B in comparative example 1were measured.

As a result, the absorption peak wavelength of the dispersion B ofcomparative example 1 was 760 nm, and the full width at half maximum ofthe absorption peak was 160 nm. The obtained results are shown by brokenlines in FIG. 3.

Example 2

10 parts by weight of the hexaboride α fine particles used in example 1,80 parts by weight of toluene and 10 parts by weight of a dispersant(acrylic polymer dispersant having amino group) were mixed to prepare 3kg of a slurry. This slurry was charged into the bead mill together withthe beads, and the slurry was circulated and pulverized and dispersedfor 50 hours.

The used bead mill was a horizontal cylindrical annular type(manufactured by Ashizawa Co., Ltd.), and the material of the inner wallof the vessel and the rotor (rotary stirring part) was ZrO₂. For thebeads, beads made of YSZ having a diameter of 0.3 mm were used.Pulverization and dispersion treatment was performed at a slurry flowrate of 1 kg/minute.

By setting the rotation speed of the rotor at 4 m/sec and making itslower than usual producing conditions, it is possible to control thedestruction mode of hexaboride α, and to control the assembly of thehexaboride fine particles contained in the fine particle dispersion ofthe hexaboride α in such a manner that when the number ratio of thehexaboride fine particles having an aspect ratio of 1.5 or more and lessthan 4.0 was expressed as a (number) %, and the number ratio of thehexaboride fine particles having an aspect ratio of 4.0 or more and lessthan 20.0 was expressed as b (number) %, 60 (number) %≦(a+b) (number)%≦100 (number) % and a:b=20:80 to 80:20 were satisfied.

The average dispersed particle size of hexaboride α in the obtainedhexaboride α dispersion (sometimes referred to as “dispersion C” in thepresent specification) was measured and found to be 23 nm.

The dried body of the dispersion C was observed by three-dimensionalimage analysis using TEM tomography in the same manner as in example 1.As a result, it was found that 26.9 (number) % of hexaboride α fineparticles having an aspect ratio of 1.5 or more and less than 4.0, and72.5 (number) % of hexaboride α fine particles having an aspect ratio of4.0 or more and less than 20.0 were contained in the dispersion C.

Next, the optical properties of the dispersion C were measured.Specifically, the procedure was as follows.

In dispersion C, toluene was added so that the concentration ofhexaboride α was 0.002 mass %, diluted, mixed, and shaken well.Thereafter, the diluted solution was placed in a glass cell having anoptical path length of 1 cm, and its transmittance curve was measuredwith a spectroscope. At this time, the baseline of the spectroscope waspulled with a sample filled with toluene in the same glass cell. Next,the same operation as in the dispersion A in example 1 was performed,and the optical properties of the dispersion C in example 2 weremeasured. As a result, the absorption peak wavelength of the dispersionC of example 2 was found to be 1055 nm, and the full width at halfmaximum of the absorption peak was found to be 410 nm.

CONCLUSION

From the results in FIG. 3, it was found that dispersion A of example 1containing 36.2 (number) % of hexaboride α fine particles having anaverage dispersed particle size of 21 nm and an aspect ratio of 1.5 ormore and less than 4.0, and 63.3 (number) % of hexaboride α fineparticles having an aspect ratio of 4.0 or more and less than 20.0, hasa wide range of near-infrared absorption with a peak at a wavelength of985 nm corresponding to near infrared, and good solar radiationshielding characteristic was exerted. Also, dispersion C of example 2containing 26.9 (number) % of hexaboride α fine particles having anaverage dispersed particle size of 23 nm and an aspect ratio of 1.5 ormore and less than 4.0, and 72.5 (number) % of hexaboride α fineparticles having an aspect ratio of 4.0 or more and less than 20.0, alsoexerted a similar solar radiation shielding characteristic.

In contrast, dispersion B of comparative example 1 containing hexaboridefine particles having an average dispersed particle size of 27 nm and anaspect ratio of 1.0 or more and 1.5 or less, was located at a wavelengthof 760 nm where the absorption peak corresponds to visible light, andthe full width at half maximum was also small. That is, although it hada sharp absorption near the wavelength of 700 to 800 nm, the absorptionof near infrared light in the region longer than the wavelength of 800nm was weak. Therefore, compared with the dispersions A and C ofexamples 1 and 2, the solar radiation shielding characteristic wasinferior.

1-16. (canceled)
 17. An assembly of hexaboride fine particles, whereinwhen a particle shape of the hexaboride fine particles contained in theassembly is regarded as a spheroid body, and when the number ratio ofthe hexaboride fine particles contained in the assembly and having anaspect ratio [(long axis length)/(short axis length)] of 1.5 or more andless than 4.0 is expressed as a (number) %, and the number ratio ofhexaboride fine particles contained in the assembly and having an aspectratio [(long axis length)/(short axis length)] of 4.0 or more and lessthan 20.0 is expressed as b (number) %, 60 (number) %≦(a+b) (number)%≦100 (number) %, and a:b=20:80 to 80:20 are satisfied.
 18. The assemblyof hexaboride fine particles according to claim 17, wherein thehexaboride fine particles contained in the assembly of the hexaboridefine particles have an average dispersed particle size of 1 nm or moreand 100 nm or less.
 19. The assembly of hexaboride fine particlesaccording to claim 17, wherein the hexaboride fine particles arelanthanum hexaboride fine particles.
 20. A hexaboride fine particledispersion, containing the assembly of the hexaboride fine particlesaccording to claim 17 in a state of being dispersed in a liquid medium,the liquid medium being selected from water, an organic solvent, an oiland fat, a liquid resin, a liquid plasticizer for a plastic, or amixture of two or more selected from them.
 21. The hexaboride fineparticle dispersion according to claim 20 wherein the hexaboride fineparticles are contained in an amount of 0.02 mass % or more and 20 mass% or less.
 22. A hexaboride fine particle-dispersed body, wherein theassembly of the hexaboride fine particles of claim 17 are dispersed in athermoplastic resin or a UV curable resin.
 23. The hexaboride fineparticle-dispersed body according to claim 22, wherein the thermoplasticresin is one kind of resin selected from the group consisting ofpolyethylene terephthalate resin, polycarbonate resin, acrylic resin,styrene resin, polyamide resin, polyethylene resin, vinyl chlorideresin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylenevinyl acetate copolymer, and polyvinyl acetal resin; or a mixture of twoor more kinds of resins selected from the resin group; or a copolymer oftwo or more kinds of resins selected from the resin group.
 24. Thehexaboride fine particle-dispersed body according to claim 22, whereinthe hexaboride fine particles are contained in an amount of 0.001 mass %or more and 80.0 mass % or less.
 25. The hexaboride fineparticle-dispersed body according to claim 22, wherein the hexaboridefine particle-dispersed body has a sheet shape, a board shape, or a filmshape.
 26. The hexaboride fine particle-dispersed body according toclaim 22, wherein the content of the assembly of the hexaboride fineparticles per unit projected area contained in the hexaboride fineparticle-dispersed body is 0.01 g/m² or more and 0.5 g/m² or less.
 27. Alaminated transparent base material using hexaboride fineparticle-dispersed body, wherein the hexaboride fine particle-dispersedbody of claim 22 is present between a plurality of transparent basematerials.
 28. An infrared absorptive film or an infrared absorptiveglass, wherein the hexaboride fine particle-dispersed body of claim 22is provided as a coating layer on at least one side of a transparentbase material selected from a transparent film base material or atransparent glass base material.
 29. An infrared absorptive film or aninfrared absorptive glass according to claim 28, wherein the resin is aUV curable resin.
 30. The infrared absorptive film or the infraredabsorptive glass according to claim 28, wherein the thickness of thecoating layer is 10 μm or less.
 31. The infrared absorptive filmaccording to claim 28, wherein the transparent film base material is apolyester film.
 32. The infrared absorptive film or the infraredabsorptive glass according to claim 28, wherein the content of thehexaboride fine particles per unit projected area included in thecoating layer is 0.01 g/m² or more and 0.5 g/m² or less.